Cam-and-groove couplings are used to connect fluid lines. A conventional cam-and-groove coupling consists of a female part, a male part and at least one locking arm, The female part and male part are annular walls. The male part is shaped to slidingly insert into and withdraw from the female part and has a groove formed circumferentially on its outside surface. The female part has at least one aperture in its wall. The locking arm is rotatably connected to the female part and has a cam on its surface that is shaped to engage the groove of the male part. When the male part is inside the female part, the locking arm is rotatable between a locked position in which the cam protrudes through the aperture and lockingly engages the groove to sealably connect the male part to the female part, and an unlocked position in which the cam is substantially outside of the female part and thus permits the male part to withdraw from the female part.
When the locking arm of a conventional cam-and-groove coupling is in the unlocked position, the male part may accidentally withdraw from the female part because the male part is retained in the female part only by relatively low friction between the two parts. Such friction may be overcome by the residual fluid pressure in the fluid lines or the weight of the fluid lines when they are inclined or unsupported. This separation can result in fluid spillage, which is especially undesirable if the fluid is hazardous or contaminating to the environment. Further, if the fluid pressure is significant, the separation may occur violently and pose a risk of bodily injury or property damage.
In the prior art, modifications to cam-and-groove couplings and other types of lockable couplings permit the female part to retain the male part. U.K. Patent Application GB 2,211,258 to Marshall, U.S. Pat. No. 7,988,200 to Krywitsky, PCT International Application WO 2011/139152 to Andries et al., and the “PT Pressure Safe” cam-and-groove coupling invented by Paul Schwindt and Alan Littlefield and marketed by PT Coupling® each disclose connections in which a pin formed on the surface of one or both of the male part, or the female part, engages a compatible channel formed in the wall of the other part. Such designs have several potential disadvantages including that the pin and channel may complicate the manufacturing of the coupling, may create additional stress concentrations in the wall, and may deform or weaken with repeated use or abuse.
Accordingly, there remains a need for a modified cam-and-groove coupling where the female part retains the male part even when the locking arm is in the unlocked position.